NOVA put together a video, embedded below, about one of those animals that you have to keep persuading yourself is real, a parasitic crustacean that lives inside the mouths of fishes, eating–and then taking the place of–its host’s tongue.

I can vouch for these beasts, having written about them off and on since I first encountered them in my research for Parasite Rex–most recently on the Loom last year. But I was not aware that it’s the female that wins the Oscar for best performance as a fish tongue. The males just hang out around the gills of the fish and then–yep–mate with the pseudo-tongue.

Clownfish with parasitic isopod. Copyright Lea Lee. http://www.flickr.com/photos/critter71/

This discovery led me to wonder about the latest research about tongue-eating isopods. I came across a 2012 master’s thesis by Colt William Cook of the University of Texas, which confirms what you see in the video–that the parasites are born as males, and then when they enter a fish, one turns female. This switch only occurs if there’s no female already installed in the host–otherwise, the males stay male. As this transformation takes place, Cook adds, the female’s body grows enormously. Its eyes shrink, since it no longer has to hunt for a home. Its legs stretch out, to help it anchor itself in the mouth.

Courtesy of Matthew Gilligan

After one of the males mates with the female, she gives birth to a brood of live male parasites. For their first few days, Cook found, they search madly for another host (each species of parasite seems to only live in a single species of fish). They sniff for the scent of their host, and if a shadow passes overhead when the odor is strong, they shoot upwards through the water. They burn through a lot of energy in the process; if they fail to find a host in the first few days, they settle down and hope they can ambush a fish that happens to be swimming by. It’s a hard way to start your life, and it may explain why several males will huddle inside a fish with only a single female in the offing. Looking for another fish with a single female parasite might be a less promising strategy than competing with the males you’re with.

Of course, these rules may only apply to the species that Cook studied, which infects Atlantic croakers off the coast of Florida. The full diversity of these tongue parasites is probably enormous. A 2012 study puts the total species at 280, but that’s just known species. A team of scientists from Annamalai University in India recently did a survey of the parasites in fishes off the coast of India. Before their study, scientists knew of 47 species of parasites in Indian waters. In just nine fishes, the scientists discovered ten new parasite species. I’d wager that some of the species waiting to be discovered will prove to be even more surreal.

[Clownfish photo: Copyright Lea Lee. via Flickr ]

Scientists map tapeworm DNA

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Scientists said Wednesday they had unravelled the genetic code of the tapeworm, unearthing data that should lead to more efficient drugs against the dangerous intestinal parasite.

Tapeworms are among the first known parasites of humans, recorded by Hippocrates and Aristotle as long ago as 300 BC.

Published in the journal Nature, the research highlighted genetic similarities between tapeworms and cancer tumours.

The finding suggests existing cancer drugs that suppress cell division and prevent DNA replication point to a novel cure, which would save time and money in development, the authors said.

“These genome sequences are helping us to immediately identify new targets for much-needed drug treatment,” Matthew Berriman of the Wellcome Trust Sanger Institute said in a statement.

People contract tapeworms by ingesting their eggs or larvae, found in raw or undercooked meat of an infected animal or freshwater fish, contaminated water or through close contact with an infected person or livestock. Areas of poor sanitation pose the highest risk.

Some larvae settle in the human intestine and become adult worms of up to three metres (10 feet) long. The infestation can be easily treated with two standard drugs.

But the larvae can also migrate to other body parts, where they continue to develop and are harder to spot and treat. Larvae cysts in the eyes can cause blindness, while cysts in the brain are a major cause of epilepsy in the developing world and are potentially life-threatening.

“Tapeworm infections are prevalent across the world and their devastating burden is comparable to that of multiple sclerosis or malignant melanoma (skin cancer),” said Berriman.

The tapeworm is specially adapted to parasitism, it has no gut, head or light-sensing organs, but has a unique surface able to withstand its host’s digestive acids while still absorbing nutrients.

Berriman and a team of researchers mapped the genomes of four types of tapeworm and discovered they all lacked the ability to synthesise fatty acids and cholesterol that are crucial for larvae development — instead scavenging these from the host.

An effective treatment could thus be to target the genes and proteins involved in the scavenging process, they wrote.

The team also discovered why drugs that target enzymes in the central nervous system of other flat worms had not been effective: tapeworms produce few of these vital proteins.

“Our data will serve as a ‘parts list’ for tapeworm scientists to explore and identify vulnerabilities over a much, much shorter timeframe,” Berriman told AFP.

“The study identifies some of the vulnerabilities already, such as parts of metabolism that the parasite is highly dependent on.”

Scientists map tapeworm DNA

Share on facebookShare on redditShare on diggShare on twitterShare on farkShare on stumbleupon2

 

Scientists said Wednesday they had unravelled the genetic code of the tapeworm, unearthing data that should lead to more efficient drugs against the dangerous intestinal parasite.

Tapeworms are among the first known parasites of humans, recorded by Hippocrates and Aristotle as long ago as 300 BC.

Published in the journal Nature, the research highlighted genetic similarities between tapeworms and cancer tumours.

The finding suggests existing cancer drugs that suppress cell division and prevent DNA replication point to a novel cure, which would save time and money in development, the authors said.

“These genome sequences are helping us to immediately identify new targets for much-needed drug treatment,” Matthew Berriman of the Wellcome Trust Sanger Institute said in a statement.

People contract tapeworms by ingesting their eggs or larvae, found in raw or undercooked meat of an infected animal or freshwater fish, contaminated water or through close contact with an infected person or livestock. Areas of poor sanitation pose the highest risk.

Some larvae settle in the human intestine and become adult worms of up to three metres (10 feet) long. The infestation can be easily treated with two standard drugs.

But the larvae can also migrate to other body parts, where they continue to develop and are harder to spot and treat. Larvae cysts in the eyes can cause blindness, while cysts in the brain are a major cause of epilepsy in the developing world and are potentially life-threatening.

“Tapeworm infections are prevalent across the world and their devastating burden is comparable to that of multiple sclerosis or malignant melanoma (skin cancer),” said Berriman.

The tapeworm is specially adapted to parasitism, it has no gut, head or light-sensing organs, but has a unique surface able to withstand its host’s digestive acids while still absorbing nutrients.

Berriman and a team of researchers mapped the genomes of four types of tapeworm and discovered they all lacked the ability to synthesise fatty acids and cholesterol that are crucial for larvae development — instead scavenging these from the host.

An effective treatment could thus be to target the genes and proteins involved in the scavenging process, they wrote.

The team also discovered why drugs that target enzymes in the central nervous system of other flat worms had not been effective: tapeworms produce few of these vital proteins.

“Our data will serve as a ‘parts list’ for tapeworm scientists to explore and identify vulnerabilities over a much, much shorter timeframe,” Berriman told AFP.

“The study identifies some of the vulnerabilities already, such as parts of metabolism that the parasite is highly dependent on.”